A 3D model of a terrain landscape made in Blender with proper PBR (Physically Based Rendering) materials would typically consist of a highly detailed terrain mesh, with intricate textures and materials that are designed to mimic the appearance and behavior of real-world materials.
The terrain mesh itself is created using a combination of sculpting tools and heightmap data from google, which is used to generate a detailed landscape with hills, valleys, mountains, and other natural features. Carefully made to match the real-world appearance of the terrain.
These materials are created using a combination of physically accurate models and artistic techniques, such as roughness, metallicness, and normal mapping, which is used to create the appearance of different surface properties like roughness, reflectivity, and other characteristics that make the terrain look more realistic